The invention relates to stable emulsions comprising salicylic acid and acrylates/C10-C30 alkyl acrylate cross polymers which are used in combination with a substrate to form a wipe product that effectively delivers salicylic acid to the skin while being mild to the skin.
Commercial aqueous based facial wipes which contain salicylic acid require either a high level of polyol (such as glycerol or propylene glycol), or ethanol to solubilize the salicylic acid. Unfortunately, formulations with high levels of polyol are perceived by consumers to have poor aesthetic properties (when compared to emulsion type products), while high levels of ethanol can cause irritation to the skin.
Commercial emulsions manufactured for wipe products are preferred to have a viscosity less than 1000 cps to enable impregnation in the conventional manner. Current formulation trends require a complex mixture of surfactants and emulsifiers and emulsification temperatures above 60xc2x0 C. to incorporate oil phases to produce impregnates at such a viscosity.
Commercial lotions containing salicylic acid and acrylates/C10-30 alkyl acrylate cross polymers are stabilized by the use of high quantities of emulsifier (usually emulsifiers which are solid at room temperature) and medium to high viscosity to prevent phase separation. A typical viscosity for such a lotion ranges from about 20,000 to about 100,000 cps.
Emulsions formed by acrylates/C10-30 alkyl acrylate cross polymers (in particular those anionic in nature, with a hydrophilic backbone and hydrophobic portions to xe2x80x9clockxe2x80x9d the oil in place) are sensitive to salts and soluble cations. The addition of salicylic acid to emulsions containing only acrylates/C10-30 alkyl acrylate cross polymers solutions as an emulsifier causes immediate instability and results in separation of the oil and aqueous phase (creaming) or release of the oil phase from the polymer (coalescence) at a pH less than 7.
U.S. Pat. No. 5,648,083 describes personal care compositions including silicones and polymeric emulsifier for providing barrier protection against dermatitis for baby wipes. The compositions do not incorporate cationic species, such as salicylic acid or non-ionic surfactants to modify the surface tension and interact with polymeric emulsifier and oil droplets.
A study released by B F Goodrich, investigating the stability of a cationic surfactant in combination with Pemulen (an acrylates/C10-30 alkyl acrylate cross polymer) states that at a pH of 5.5 the maximum concentration of cationic surfactant that remains compatible with the polymer is less than 0.25% by weight, despite increases in polymer concentration from 0.2 to 0.6%. Additional figures show that at higher pH (7.0), stability can be achieved above a viscosity of 1000 mpas. See PEMULEN Polymeric Emulsifiers, xe2x80x9cCationic Skin Lotions Formulated with PEMULEN Polymeric Emulsifiersxe2x80x9d, 1995.
Polymeric Emulsifiers, xe2x80x9cAn Alternative to Traditional Emulsifiers based on Stability of Multi-Phase Systemsxe2x80x9d, Daniella R. J. Clymans, Hans M. Brand, B. F. Goodrich Chemical, discusses the use of small chain nonionic surfactants such as Poloxamer 181 (at 0.05-0.2% by weight) or similar products and the use of ethoxylated/propoxylated fatty alcohols to adjust surface properties (such as xe2x80x9cquick break effectxe2x80x9d) and the rheology of PEMULEN emulsions. According to the article these surfactants do not act as emulsifiers, but only reduce the surface tension of the dispersed oily phase at the use level of 0.05-0.2 and by weight.
Accordingly, there remains a need for a stable emulsion including salicylic acid and acrylates/C10-30 alkyl acrylate cross polymers.
The invention relates to a wet wipe product comprising a substrate and an emulsion. The emulsion comprising: an acrylate/C10-C30 alkyl acrylate cross polymer emulsifier; salicylic acid; a nonionic surfactant; and a lipophillic component. The nonionic surfactant is selected from the group consisting of (i) a polymeric ether, (ii) a mixture of laurate esters of sorbitol and sorbital anhydrides condensed with ethylene oxide; and (iii) mixtures thereof.
The invention also relates to a method for depositing salicylic acid to mammalian skin comprising topically applying the wipe product described above to the skin to be treated.
The emulsion according to the invention produces an aesthetically pleasing product, capable of removing non-water proof make-up and able to deliver salicylic acid to the skin and is mild on the skin.
As discussed above, the invention relates to a wet wipe product comprising a substrate and an emulsion, said emulsion comprising:
(a) an acrylate/C10-C30 alkyl acrylate cross polymer emulsifier;
(b) salicylic acid; and
(c) a nonionic surfactant selected from the group consisting of (i) polymeric ether, (ii) a mixture of laurate esters of sorbitol and sorbitol anhydrides condensed with ethylene oxide; and (iii) mixtures thereof.
The acrylate/C10-C30 alkyl acrylate cross polymer is a white solid powder commercially available from B F Goodrich under the name PEMULEN. It is a high molecular weight cross linked poly(acrylic acid) polymer which contains a hydrophilic back bone and hydrophobic portions which stabilize the oil and lock it in place. The polymer is anionic in nature and can be the only emulsifier used to emulsify the lipophillic components. In a preferred embodiment the acrylates/C10-C30 alkyl acrylate cross polymer is present in an amount ranging from about 0.05 to about 2.0% by weight, more preferably from about 0.12 to about 0.13% by weight.
The emulsions of the present invention further comprise at least one emulsion stabilizer. Examples of suitable emulsion stabilizers include small chain nonionic surfactants, such as polymeric ethers, including, for example, polyoxyethylene-polyoxypropylene block polymers and nonionic surfactant consisting of a mixture of laurate esters of sorbitol and sorbitol anhydrides, condensed with approximately ethylene oxide. Particularly preferred nonionic surfactants useful as emulsion stabilizers include (1) Poloxamer 124 : A non-ionic surfactant which belongs to the chemical class of polymeric ethers, consisting of a polyoxyethylene, polyoxypropylene block polymer and (2) Polysorbate 20: a nonionic surfactant consisting of a mixture of laurate esters of sorbitol and sorbitol anhydrides, condensed with approximately 20 moles of ethylene oxide.
Although not wishing to be bound by any theory, the proposed mechanism of stabilization is (1) by protection of the hydrophilic backbone by the small chain non-ionic particles to hinder shrinkage and reactions to the salicylic acid; (2) stabilization of the oil droplet at the C10-C30 alkyl acrylate cross polymer/lipophillic interface by lowering the surface tension and hence nullifying the effects of salicylic acid.; or a combination of both 1 and 2.
In a particularly preferred embodiment, the nonionic surfactant is a mixture of (i) a polyoxyethylene-polyoxypropylene block polymer and (ii) a mixture of laurate esters of sorbitol and sorbital anhydrides condensed with 20 moles of ethylene oxide and is present in amount ranging from about 0.01 to about 10.0% by weight, preferably from about 0.03 to about 0.08% by weight.
The emulsions used in the wipe product of the invention further comprise a cationic active ingredient such as salicylic acid. Preferably, salicylic acid is incorporated for its keratolytic action for the prevention and treatment of comodons and for its slight antibacterial properties. Suitable amounts of salicylic acid range for example, from about 0.05 to about 0.5% by weight, preferably from about 0.05 to about 0.5% by weight.
The emulsions of the invention further comprise a lipophillic component to contribute to the aesthetics of the product. Suitable lipophillic components include as emollients such as C12-C15 alkyl benzoate; cyclomethicone, dimethicone, and mixtures thereof. The emollients are generally present in an amount ranging from about 0.05 to about 20.0% by weight. In a preferred embodiment, the emulsions according to the invention comprise from about 0.05 to about 0.5% by weight, preferably, from about 0.05 to about 0.2% by weight, of cyclomethicone, from about 0.05 to about 0.5% by weight, preferably from about 0.05 to about 0.2% by weight, of dimethicone, and from about 0.05 to about 20.00% by weight, preferably, from about 0.05 to about 1.00% by weight of C12-C15 alkyl benzoate.
As discussed above, the emulsions used in the wipe product according to the invention are mild to the skin and aesethically pleasing due to the low concentration of alcohols, such as ethanol, polyols and surfactants. However, the wipe product according may comprise an effective amount of a water-soluble polyol. Water-soluble (which includes water-miscible) polyols are polyols that are able to uniformly dissolve or disperse in water. The water-soluble polyol may serve several purposes in the composition. For example, the polyol may function as a skin moistener, humectant, or emollient The polyol may be used as a solvent for one or more components of the composition.
Water-soluble polyols that are suitable for use herein are taught for example by U.S. Pat. No. 5,648,083, the disclosure of which is hereby incorporated by reference. Suitable water-soluble polyols include water-soluble alkylene polyols and water-soluble analogs of such polyols. Water-soluble analogs of these polyols include water-soluble esters of alkylene polyols. Non-limiting examples of water-soluble polyols suitable for use herein include ethylene glycol, propylene glycol, butylene glycol, diethylene glycols, triethylene glycols, other water-soluble polyethylene glycols, water-soluble soluble polypropylene glycols, hexylene glycol, glycerol, polyoxyethylene sorbitol, 1,2,4-butane triol, 1,2,6-hexane triol, sorbitol and mixtures thereof.
Generally, the polyol or humectant is present in amounts ranging from about 0.5 to about 20% by weight, preferably from about 0.5 to about 5% by weight, most preferably from about 0.5 to about 2% by weight. The compositions of the invention can comprise less than 5% by weight of a polyol and can be free from ethanol.
The emulsions according to the invention may optionally contain an effective amount of any of the preservatives known in the art. Examples of suitable preservatives include phenoxyethanol, methylparaben, ethylparaben, propylparaben, butylparaben, isobutylparaben, and mixtures thereof. A particularly preferred preservative is PHENONIP which is a mixture of phenoxyethanol, methylparaben, ethylparaben, propylparaben, and butylparaben commercially available from Nipa Laboratories, Inc.
Another optional component useful in the emulsions according to the invention is any of the anti-irritants known in the art. The anti-irritant should be present in an amount effective to provide anti-irritation properties to the compositions. An example of a suitable anti-irritant is allantoin which is generally present at from about 0.05 to about 2.00% by weight, more preferably, from about 0.05 to about 0.5% by weight.
The inclusion of small chain non-ionic surfactants at low levels, stabilizes the polymeric emulsifier at a pH less than 7 for incorporation into fabric. In one embodiment, the pH of the emulsion of the invention can range from about 4.0 to about 5.5. The pH can be adjusted by adding one or more pH-adjusting agents in an amount effective to provide such pH values (herein alternatively referred to as xe2x80x9can effective amountxe2x80x9d). Agents that may be used to adjust the pH of the compositions herein include organic and inorganic acids and bases. An example of a suitable base is sodium hydroxide. The viscosity is less than 1000 cps which allows for impregnation into fabric in the conventional manner.
Exemplary preferred compositions of the present invention include the ingredients and ranges of concentrations set forth in Table 1 below:
The compositions may be prepared by oil-in-water emulsion techniques such as are known or become known in the art, such as taught, for example, by U.S. Pat. No. 5,648,083, the disclosure of which is hereby incorporated by reference. In general, the process involves the steps of preparing a mixture of the ingredients of the composition and subjecting the mixture to conditions to cause the formation of a homogeneous and stable oil-in-water emulsion (a suspension of the silicone oil in the water and water-soluble materials is formed). Homogeneity is indicated by a composition which is substantially smooth, lump-free and uniform in appearance. A stable emulsion remains homogeneous over a given period which is determined by the required shelf life of the composition.
As used herein, xe2x80x9cwipe productxe2x80x9d means a substrate and a composition of the present invention which are pre-combined for later use. Suitable wipe substrates include those known in the art such as nonwovens, films, foams, sponges, and the like, as taught for example by U.S. Pat. Nos. 5,648,083, 3,905,863, 3,974,025, and 4,191,609. Each of these references are incorporated herein by reference in their entirety. Preferred wipe substrates comprise a porous material which is capable of holding the composition within the pores of the substrate.
Techniques for combining wipe substrates with a cleansing or treating composition, and for their packaging are well known in the art and are applicable to the present invention. In general, the wipe substrate is combined with the composition by one or more techniques involving coating, immersing, dipping, spraying, extruding, and the like. In general, the wipes are combined with an amount of the composition sufficient to provide good effective cleansing.
The use of the polymeric emulsification system allows for cold process manufacture, which in effect, decreases batch cycle time, decreases equipment requirements of manufacturer (heated vessels not required) and hence decreases the costs to manufacture.
The use of the polymeric emulsifier has also produced an aesthetically pleasing product which delivers salicylic acid to the skin, yet has been proven by clinical testing to be mild on skin. Accordingly, in another embodiment the invention relates to a method for depositing salicylic acid to mammalian skin comprising topically applying a wipe product comprising an emulsion comprising: an acrylate/C10-C30 alkyl acrylate cross polymer emulsifier; salicylic acid; a nonionic surfactant; and a lipophillic component. The nonionic surfactant is selected from the group consisting of (i) a polymeric ether, (ii) a mixture of laurate esters of sorbitol and sorbital anhydrides condensed with ethylene oxide; and (iii) mixtures thereof. The emulsion can be used as a xe2x80x9cleave onxe2x80x9d composition or rinsed from the skin with water.